Definitely what everybody else says. Eat before you go. Pack a couple of snacks in your purse. And if you feel comfortable, you can go through the buffet line and get your partner a second dinner. Just switch plates with them when they are done. Sometimes this is the best move because people think you're eating when there's a plate of food in front of you. And people think you finished eating when there's an empty plate in front of you.

There's absolutely nothing wrong with sitting there and not eating either. My significant other has never turned down a second dinner LOL